Chapter 26 Quarantine of Fish and Aquatic Invertebrates in Public Display Aquaria
Quarantine reduces the risk of introducing infectious diseases into established collections. For fish and aquatic invertebrates, key components are the provision of excellent water quality and a suitable environment, isolation from collection animals, and easy access to allow monitoring, as well as diagnostics and treatments where necessary.7,11,20 Methods will depend on the needs of the institution, facilities available, species acquired, and condition of the animals. This chapter will focus on quarantine within closed, or recirculating, systems in public display aquaria.
Shipments vary from one large specimen to several thousand small fish. Animals may come from other zoos and aquaria or be wild-caught by the institution, but they usually come from distributors. Many common freshwater fish are bred in captivity; the more unusual freshwater species and most marine species are wild-caught. Sources and shipping are not discussed in this chapter but using a reliable source, excellent shipping conditions, and the shortest shipping times will improve quarantine success.
Common Problems
Some of the more common problems seen in quarantine are as follows7,11,13–16,19:
General Planning
An ideal quarantine area is one isolated from the established collection, such as in a separate building or area, with dedicated staff.3 If this is not possible, protocols should be in place to prevent cross-contamination (e.g., isolated systems, lids on tanks, separate equipment, hand washing facilities) and the area should have minimal through-traffic.
For smaller systems, sponge filters are ideal. Larger systems usually include sand filters and biotowers.13,19 If systems are periodically unoccupied, protocols should exist to maintain biologic filtration, such as routine dosing with ammonium chloride. Undergravel filters (and substrate in general) should be avoided, because parasites and intermediate hosts may collect in substrate. Ultraviolet (UV) filtration may help reduce bacterial and viral load in the water. Ozone is generally not practical in quarantine systems because of the variable bioload. Filters with activated carbon or zeolite clay should be available for adsorption of drugs following immersion treatment. There should be redundancy in the life support equipment in case of failure. Disposal of waste water, in-water medications, and filter media should follow relevant regulations.
The Association of Zoos and Aquariums (AZA)–recommended minimum quarantine duration is 30 days.3 At the National Aquarium, quarantine for fish not treated for protozoal ectoparasites is a minimum of 90 days; some pathogens have presented up to 65 days into quarantine (e.g., Amyloodinium in temperate species).
A wide variety of good-quality foods should be available, including pelleted and flake foods, gel foods (e.g., Mazuri Gel diets), frozen foods (e.g., fish, crustaceans, mollusks), algae sheets, leafy greens, and vegetables.7 It may be hard to convert some wild-caught animals to a captive diet, and they may not have eaten recently. Most facilities maintain some live foods to encourage food intake, such as brine shrimp, glass shrimp, rotifers, minnows, and mollies. These should be bred in-house or put through a quarantine period.
Plans for cleaning and disinfection of equipment and systems need to be established. Many types of disinfectants are available (e.g., chlorine, iodophors, quaternary ammonium, peroxygen compounds), and these should be rotated routinely.20
Considerations Prior to Acquisition and on Arrival
Prior to Acquisition
Animals should be provisionally allocated to systems based on their environmental requirements (e.g., temperature, pH, salinity, water flow, lighting), their compatibilities, and the target stocking density. Water parameters should not be changed rapidly to accommodate incoming shipments because this damages the biologic filtration. Invertebrates, teleosts, and elasmobranchs should not be quarantined in the same system because this limits treatment options. Juveniles, or any animals considered potentially sensitive to treatments, should not be housed with large groups of other fish. Stocking densities should be kept low to decrease competition and disease transmission. Based on a review of quarantine data, stocking density for freshwater and salt water fish quarantine at the National Aquarium is less than 1.5 inch of fish/U.S. gallon (or 1.5 cm/liter). Some systems should remain available in case groups need to be split.
Prior to the animals’ arrival, the water quality should be checked to ensure that it is within the target range. Décor that is suitable for the species should be added, such as plastic plants at the surface for freshwater butterflyfish (Pantodon spp.). Gravel or sand may be needed for a few species, such as garden eels (Gorgasia spp.). Suitable vinyl nets or stretchers should be available.
Where animals are being acquired from another institution, a history and preshipment examinations should be obtained. Pertinent questions include whether the animals were wild-caught or captive-bred, when they were acquired, any infectious disease concerns, and water quality, diet, and behavioral information. For most shipments, however, the history is limited to the area where the animals were caught or bred.
On Arrival
Most fish and aquatic invertebrates are shipped in clear bags with water and air or oxygen, packed in an insulated container. Larger fish usually have their own transport container and may have continuous aeration and filtration. Over time, transport water shows increased ammonia levels and decreased dissolved oxygen and pH, and will gradually adapt to the ambient temperature. Unless shipping containers are badly fouled or drained, water from the target system should be gradually introduced over 20 to 60 minutes to allow the animals to adapt to the new parameters before they are moved to the new tank (acclimation). They must be closely monitored; acclimation should be shortened if there are any signs of distress (e.g., increased gilling rates, neurologic signs). Low light conditions and minimal noise may be beneficial during acclimation and the first 12 to 24 hours.
It is important to record the shipping conditions, including delays in shipping, bag condition, stocking density, and fouling. Temperature, dissolved oxygen, pH, and total ammonia of the transport water should be recorded. This information helps determine stress levels during shipment, which may affect susceptibility to infectious diseases, and may be used to compare shipping methods.
Monitoring
Regular visual examinations must continue throughout quarantine—subtle changes in behavior and food intake are usually the first signs of impending issues (Box 26-1). Monitoring sheets may be used to track essential data, such as temperature, water quality, food intake, mortalities, treatments, and drug levels, when assayed (Fig. 26-1). Water quality should be checked daily until stable and then at increased intervals. It is important to have a set of acceptable water quality parameters and protocols to correct parameters as necessary (Table 26-1).
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